NOx Emission Removal from a Parallel Diesel Engine Group by SCR System Based on Distributed Control Technology.

In industrial application, an engine group with several engines running in parallel produces emissions, and because of its variable operation conditions and the number of engines being run, it produces great pollution. This study proposes a distributed control system (DCS) method to deal with NOx emissions from a diesel engine group. This DCS method contains several diesel engine test benches in parallel, and each engine is connected to an independent DCS unit with a selective catalytic reduction (SCR) device, and the central processing unit (CPU) distributes controlling quantities to each DCS unit. A dimensionless parameter, coefficient of difficulty K, is introduced to evaluate the NOx conversion efficiency of each unit. A control algorithm adopting the minimum K as the optimization control object to distribute the real-time NOx conversion efficiency for each unit is presented. This DCS deNOx technology has been applied in 10-engine test benches in parallel, and the results show that the DCS method not only controls NOx emissions of the engine group within the emission standard limit but also exhibits a good economic performance for suitable NOx conversion efficiency distribution and economical urea injection dose. This DCS emission control method is suitable for multiple diesel engines running in parallel under conditions of varied speeds and loads.